Abstract: In this greenhouse study we investigated the effects of soil compaction and moisture stress preconditioning on stomatal diffusive resistance (Rs), leaf water potential (&#936;1), and canopy minus air temperatures (&#916;T) of Kentucky bluegrass (Poa pratensis L. ‘Ram I’). The compaction treatments were: (i) NC = no compaction, (ii) LT = long-term compaction over a 99-day period, and (iii) ST = short-term compaction for 9 days. The compactive treatment was equivalent to 720 J energy. Irrigation regimes were initiated at the same time as LT compaction and were: (i) well-watered = irrigation at &#8722;0.045 MPa and (ii) water-stressed = irrigation at &#8722;0.400 MPa. Ninety-nine days after initiation of preconditioning treatments, a dry-down cycle was started by watering each treatment to saturation. At this time, we monitored on a daily basis Rs, &#936;1, and &#916;T. Under low soil O2, Rs remained low for 2 days and then increased over a 5-day period for all treatments, even though &#936;1 did not change until the fifth day after irrigation (DAI). By DAI 9, Rs declined but then increased between DAI 10 to 13 as soil water potential (&#936;s) and &#936;1 decreased. As soil water deficits increased, plants preconditioned to LT compaction or water-stressed exhibited lower &#936;1 (0.2 to 0.4 MPa), higher Rs, and higher &#916; (1 to 2°C) compared with uncompacted or well-watered plants. Regardless of the cause for higher Rs (i.e., low soil O2, LT compaction or water-stress preconditioning), the result would be lower photosynthesis and greater high-temperature stress.